Car speakers install into your dashboard or door frame inside of a cutout in the door or dash. Only certain sized speakers fit these pre-cut holes. Installing larger or smaller speakers will not work. To install new speakers, you first size and measure the holes.
Locate the car speaker hole in your car that you intend to size.
Remove the existing speaker from the speaker hole by removing the trim by hand (it will usually unscrew or lever off with a flat screwdriver), and then unscrewing the mounting bolts on the sides of the speaker. Pull the speaker out of the frame.
Measure the distance across the speaker hole at the widest point using a tape measure. The measurement of your speaker opening will be close to three inches, four inches, 5.25 inches, 6.5 inches or 6.75 inches. Oval speakers may be four-by-six inches, five-by-seven inches or six-by-nine inches, which are standard speaker sizes for cars. Narrow your car's measurement to one closest to one of these values. That is the size of your car speakers.
Measure the distance between the holes for the mounting bolts on the speaker hole using a tape measure. The distance between the mounting bolts needs to be the same in the new speakers as for the old speakers so that you can mount the new speakers successfully by matching up the holes.
